1. Field of Invention
The present invention relates to protective structures for vehicular engine parts, such as engine exhaust manifolds for example, that generate substantial heat and vibration during engine operation. More specifically, the invention relates to fabrication of protective heat shields applied to such engine parts for insulating such parts from other components within an engine compartment of a vehicle, and particularly to a novel structure for reducing noise generated by such shields.
2. Description of the Prior Art
The exhaust manifolds of internal combustion engines in today""s modern vehicles can reach under-the-hood temperatures in the neighborhood of 1600 degrees Fahrenheit. Such high temperatures create significant risks of damage to electronic components sharing under-the-hood space with the manifolds. Thus, protection has been provided for such components via use of heat shields designed to at least partially cover up and insulate exhaust manifolds and other heat generating component. In some cases, the shields have been effective to reduce measured temperature levels to within a range of 300 degrees Fahrenheit.
One recurrent shortcoming with respect to current shield designs, however, has been with their inability to reduce or attentuate noise down to satisfactory levels. Unfortunately, the structures for producing heat shields tend to be relatively stiff and thin, and thus prone to producing echoes rather than to absorb vibrations and/or noise.
The present invention provides an improved insulated heat shield for engine components, such as exhaust manifolds of internal combustion engines. In the described embodiment, a heat shield is formed as a unitary structure adapted for securement via bolted connection to an engine manifold, and includes three layers; an outer metal layer to provide overall structural integrity, a center layer formed of an insulation material to isolate heat and to dampen noise, and an inner metal layer adjacent the shielded component for reflecting heat back to the shielded component.
In the described embodiment, the insulated heat shield includes at least one bolt aperture for attachment of the shield to an under-the-hood shielded component, such as an exhaust manifold. The bolt aperture is fully surrounded, i.e., circumferentially bordered, by at least one non-planar undulation. The undulation defines a single circular protuberance that is spaced circumferentially about the aperture in a first described embodiment. A pair of protuberances, concentric or otherwise, is situated circumferentially about the bolt aperture in a second described embodiment. Because the bolted attachment of the insulated heat shield to the manifold presents a major source of vibration transmittal from the manifold into the heat shield, the protuberance(s) is (are) effective to dampen such vibration, and hence reduce undesirable noise associated with the vibration.